Woven fabric printing ribbon having rupturable microcapsules bonded to its surface

ABSTRACT

A WOVEN FABRIC PRINTING RIBBON, COMPRISED OF INDIVIDIA; FOBERS, HAVING A MULTIPLICITY OF RUPTURABLE MICROCAPSULES BONDED TO ITS SURFACE BY MEANS OF A SOLIDIFIED FILMFORMING COACERVATE POLYMERIC MATERIAL.

States Patent Oifice 3,817,773 Patented June 18, 1974 3,817,773 WOVEN FABRIC PRINTING RIBBON HAVING RUPTURABLE MICROCAPSULES BONDED TO ITS SURFACE Richard F. Moore and Frederick C. Schiller, Centerville,

Ohio, assignors to The National Cash Register Company, Dayton, Ohio No Drawing. Filed Feb. 25, 1970, Ser. No. 14,236 Int. Cl. B41m 5/10 US. Cl. 117-361 5 Claims ABSTRACT OF THE DISCLOSURE A woven fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to its surface by means of a solidified filmforming coacervate polymeric material.

BACKGROUND OF THE INVENTION This invention relates to a woven, fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to its surface by means of a solidified film-forming coacervate polymeric material. This invention also relates to a process for bonding rupturable microcapsules to a woven fabric ribbon by means of a coacervate of a film-forming polymeric material.

The present invention provides a woven, fabric printing ribbon having a multiplicity of rupturable microcapsules bonded to its surface, the microcapsules containing and yielding on rupture a mark-forming material for use in situ in the woven, fabric ribbon where released or for transfer to another surface. A preferred use for the woven, fabric printing ribbon of the present invention is a typewriter ribbon.

Rupturable microcapsules having walls of hydrophilic polymeric material are disclosed in US. Pat. 2,800,457 issued July 23, 1957 on application of Barrett K. Green and Lowell Schleicher, and US. Pat. 2,800,458 issued on the same day on application of Barrett K. Green and which was subsequently reissued as US. Pat. Re. 24,899 on Nov. 29, 1960. The capsules of these patents are of microscopic size and have as the contents an oily material which is released by physical rupture of the microcapsules, such as by pressure. Among the uses of such microcapsules, as indicated in the patents, is to retain marking materials which make marks on paper or other record material. Paper coated with such microcapsules is disclosed in US. Pats. 2,730,456 and 2,730,457 issued on application of Barrett K. Green and Lowell Schleicher on Jan. 10, 1956.

Mark-forming sheet materials embodying microcapsules, such as those described in US. Pats. 2,730,456 and 2,730,457, have proven commercially successful and have been the practiced art in what is often referred to as carbonless carbon-paper systems. In these patents, pressure-rupturable microcapsules containing one of the markforming components are coated onto a sheet material, such as finished paper, to provide, as the case may be, either a self-contained sheet material or a transfer sheet material. The sheet material in the instance of the selfcontained system, also contains at least one other reactive mark-forming component, so that, upon application of marking pressure to the system, a mark is produced either on the sheet bearing the microcapsules, in the case of the self-contained unit, or on a receiving sheet, in the case of the transfer system. In the systems referred to above, the microcapsules are coated on a finished paper, from an aqueous dispersion of microcapsules by means of rollers, sprays, brushes, or any other of the commonly used methods of coating paper. The microcapsule coating is then allowed to dry and the dried microcapsule coating is of such a nature that the microcapsules are adherent to each other in the coating and adhere to the paper without the addition of a binder material.

Microcapsules will not adhere to a woven fabric ribbon in the same manner as they will adhere to a sheet of paper because of the nature of the construction of a woven fabric ribbon. When microcapsules are applied to a Woven fabric ribbon in the same manner as they are applied to a sheet of paper, the dried coating of microcapsules can easily be brushed or shaken off the woven fabric ribbon. The microcapsules, therefore, must be bonded to the woven fabric ribbon to provide a woven fabric printing ribbon which can utilize the advantages provided by the rupturable microcapsules.

The film-forming polymeric material which is used in the present invention to bond a multiplicity of microcapsules to a woven fabric ribbon is related to the film-forming polymeric material which is used in US. Pat. 3,384,- 536 issued May 21, 1968 on application of Robert W. Sandberg et a1. and pending US. Patent Application Ser. No. 653,755 filed July 17, 1967 by Isidore L. Yurkowitz, now Pat. No. 3,565,753. In the Sandberg et al. process, microcapsules are bonded to cellulose paper fibers when the microcapsules are brought into contact with a moving web of the fibers on a paper-making machine during a paper-making process. In the Yurkowitz process, microcapsules are bonded to cellulose paper fibers when the microcapsules are brought into contact with a slurry of the fibers prior to the paper-making process. The present invention is not related to a paper-making process. In the present invention, the microcapsules are bonded to a woven, fabric ribbon and are not bonded to a paper or paper-forming substrate. Furthermore, in the present invention, microcapsules are bonded to individual fibers of a woven fabric ribbon, after the fibers are woven into a fabric ribbon, and there is no bonding of the microcapsules to the individual fibers which form the woven fabric ribbon either prior to or during the weaving of the fabric ribbon.

The microcapsules bonded to the surface of the woven, fabric printing ribbon of the present invention contain a mark-forming material. Such a woven, fabric printing ribbon offers the advantage of having controlled release of the mark-forming material for improved print quality and greater uniformity throughout print life since the mark-forming material is not released from the microcapsules until they are ruptured by suitable means such as the impact from typewriter type. The woven, fabric printing ribbon offers further advantages of minimum aging of the mark-forming material and the use of a volatile mark-forming material since the mark-forming material is protected and preserved by microencapsulation prior to rupture of the microcapsules. Finally, thewoven, fabric printing ribbon is dry prior to its use, since the mark-forming material is microencapsulated, thereby providing clean handling characteristics at the time of installation. The preferred use for the woven, fabric print ing ribbon of the present invention is a typewriter ribbon.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a Woven, fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to individual fibers at the surface of the woven, fabric ribbon by means of a solidified film-forming coacervate polymeric material. In a preferred embodiment, the microcapsules are bonded to individual fibers at the surface of the woven fabric ribbon by means of a solidified film-forming complex coacervate polymeric material which is a complex of a cationic polymeric material and an anionic polymeric material. The oppositely charged polymeric materials are brought together to form a film-forming complex coacervate polymeric material in the presence of the woven fabric ribbon.

In further accordance with the present invention, there is provided a process for producing a woven, fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to its surface which comprises applying microcapsules to the surface of a woven fabric ribbon. Then, substantially simultaneously with application of the microcapsules, a coacervate of a film-forming polymeric material is formed at the surface of the woven fabric ribbon. The coacervate envelops the microcapsules and wets individual fibers at the surface of the woven fabric ribbon thereby bonding the microcapsules to individual fibers at the surface of the woven fabric ribbon. The woven fabric ribbon is then dried thereby producing a woven, fabric printing ribbon having microcapsules bonded to its surface by means of a solidified coacervate polymeric material.

In one embodiment of the present invention, microcapsules can be applied to the surface of a woven fabric ribbon which has a film-forming polymeric material present thereon. A coacervate phase-inducing agent, preferably in aqueous solution, can then be applied to the woven fabric ribbon to form a coacervate of a film-forming polymeric material at the surface of the woven fabric ribbon. The coacervate envelops the microcapsules and wets individual fibers at the surface of the woven fabric ribbon thereby bonding the microcapsules to individual fibers at the surface of the woven fabric ribbon. The woven fabric ribbon is then dried thereby producing a woven, fabric printing ribbon having microcapsules bonded to its surface by means of a solidified coacervate polymeric material.

DETAILED DESCRIPTION OF THE INVENTION The coacervate is a relativel viscous phase of a filmforming polymeric material which has been induced to separate as such from a solution thereof by introducing into the environment one or more of many known phase separation inducing agents. The phenomenon of phase separation to produce a relatively viscous liquid phase of a film-forming polymer from a homogeneous liquid solution thereof is referred to as coacervation and the separated or generated relatively viscous liquid phase consequently is referred to as a coacervate.

Coacervation and various techniques or procedures for effecting it are generally described by H. G. Bungenberg and H. R. Kruyt in Proceedings of the Academy of Sciences of Amsterdam, Volume 32 (1929), pages 849 to 856 and by H. R. Kruyt in Colloid Science II, Elsevier Publishing Company, Inc., New York, NY. (1949), Chapters VHI and XI. Specific techniques and procedures for etfecting and using the emergence of a coacervate phase from a solution of polymeric material are further discussed and described in US. Pats. 2,800,457 and 2,800,- 458 (Reissue 24,899) which relate to the making of microcapsules.

In a preferred embodiment of the present invention, microcapsules can be bonded to the surface of a woven fabric ribbon by use of complex coacervation wherein polymeric materials of opposite electric charge co-react under appropriate conditions to cause the generation and emergence of a relatively viscous phase of the oppositely charged polymeric materials in a discontinuous state on the woven fabric ribbon. This relatively viscous phase of the oppositely charged polymeric materials is a complex coacervate polymeric material. This bonding of the microcapsules to the woven fabric ribbon can be accomplished by applying to a woven fabric ribbon a polymeric material of one electric charge, then applying microcapsules to the surface of the woven fabric ribbon, and then applying to the woven fabric ribbon a solution of an oppositely charged polymeric material to generate a complex coacervate of the polymeric materials. Thus, upon contact of the added polymeric material of the solution and the polymeric material of opposite charge on the woven fabric ribbon, a complex coacervate polymeric material separates as a relatively viscous liquid phase which, being capable of enveloping the microcapsules and wetting the individual fibers at the surface of the fabric ribbon, thereby bonds the microcapsules to individual fibers at the surface of the woven fabric ribbon. The woven fabric ribbon is then dried thereb producing a suitable woven, fabric printing ribbon having'microcapsules bonded to its sur face by a solidified coacervate polymeric material.

Suitable cationic polymeric materials for use in the present invention include polyethyleneimine, cationic starch, cationic amines, gelatin, and tertiary amines of corn starch. Suitable anionic polymeric materials for use in the present invention include copolymers of methylvinylether and maleic anhydride, polyacrylamide, deacetylated karaya gum, guar gum, locust-bean gum, gum arabic, gum tragacanth, copolymers of ethylene and maleic anhydride, casein, and dialdehyde starches.

In general, any known technique for effecting a phase separation of a viscous liquid phase and wherein the separated viscous liquid phase will form substantially on contact with the fibers of the woven fabric ribbon is satisfactory. Preferably, the separated phase forms substantially simultaneously upon contact with the fibers of the woven fabric ribbon so as to maintain substantially all of the applied microcapsules on the surface of the woven fabric ribbon.

In all procedures, the necessary concentrations and conditions to bring about the emergence of the enveloping phase may be predetermined in such a manner that at the components essential to causing the emergent phase separation are brought into operational proximity to each other, the appropriate concentrations and conditions will be present on the woven fabric ribbon to which it is desired to bond the mircocapsules.

Essentially, the system at the initiation of the bonding of the microcapsules to the woven fabric ribbon may be characterized as comprising three phases which are mutually incompatible in the sense that each phase is an identifiable phase, and further characterized respectively, as follows:

(1) a continuous liquid phase;

(2) a discontinuous phase of a multiplicity of microcapsules dispersed in the discontinuous phase (3); and

(3) a discontinuous phase of mobile entities of filmforming polymeric material dispersed in the continuous liquid phase (1) and having microcapsules dispersed therein, the entities of polymeric material binding microcapsules to the woven fabric ribbon.

Suitable mark-forming materials or inks which may be encapsulated and are useful with this invention include colored dyes and pigments and colorless color-forming dyes used alone or in combination with colored dyes. Typical colored dyes are, for example, Hysol Blue B, 1,4- bis(N-butylamino) anthraquinone and l-N-methylamino- 4-N-isopropylamino anthraquinone, both dyes sold by Patent Chemicals Incorporated of Paterson, N.J., United States of .America, Oil Black BT (Color Index No. 26150), Oil Soluble Nigrosine, Azo Blue Black, Sudan II, Sudan III; methyl violet and similar dyes. Typical colorless color-forming dyes are, for example, crystal violet lactone (CVL), benzoyl leuco methylene blue (BLMB), and N (2,5 dichlorophenyl) leucauramine and other similar dyes which become colored when adsorbed by acid clay or like acid complex aluminates. Such dyes are disclosed in US. Pats. 2,646,367; 2,714,074; Re. 23,024; and 2,828,341.

Dyes which are colorable to a distinctive color by exposure to electromagnetic radiation and which are useful in the present invention are disclosed in US. Pats. 2,953,454 and 3,024,362.

Pigments which may constitute a portion of the ink are inorganic or organic pigments such as carbon black, titania, phthalocyanine blue, and similar well-known ink pigments. Such pigments may vary in size from a few millimicrons to several microns, depending on the intended application and on the print color desired.

Microcapsules suitable for use in the present invention can be made from hydrophilic polymeric materials such as gelatin, albumin, fibrinogen, casein, agar-agar, starch, pectins, ichthyocolla, gum arabic, copolymers of methylvinylether and maleic anhydride, polyethyleneimine, copolymers of ethylene and maleic anhydride, copolymers of styrene and maleic anhydride, sodium carboxymethylcellulose, sodium alginate, cellulose acetate phthalate, starch acetate phthalate, amylose acetate phthalate and the like using aqueous systems as disclosed in U.S. Pats. 2,730,456; 2,730,457; 2,800,457; 2,800,458 (Reissue 24,899); 3,041,289; and 3,043,782.

Microcapsules also suitable for use in the present invention can be made from wall-forming polymeric materials such as ethylcellulose, cellulose nitrate, cellulose acetate phthalate, polymethyl methacrylate, copolymers of acrylonitrile and styrene, polystyrene, copolymers of acrylonitrile and vinylidene chloride, epoxy, polyvinyl acetal and the like using solvent systems such as acetone, benzene, toluene, methyl ethyl ketone and the like as disclosed in U.S. Pats. 3,155,590 and 3,415,758.

The microcapsule diameter can vary from about 2 to about 100 microns or more but usually microcapsule diameters range in size from about 5 to about 80 microns. The microcapsule wall thickness may vary from a fraction of a micron to several microns or more.

Suitable fabric ribbons for use in the present invention can be woven from a variety of fibers such as cotton, silk, wool, nylon, polyester, and the like or blends thereof. The preferred fabric ribbons are woven using a selected fiber.

PREFERRED EMBODIMENTS The following Examples illustrate the present invention and a mode of carrying out the invention.

Example I An emulsion was made, under conditions of continuous agitation, by emulsifying 210 grams of an oil comprising a mixture of chlorinated biphenyl and kerosene containing 2.6 grams of benzoyl leuco methylene blue (BLMB) and 3.2 grams of crystal violet lactone (CVL) in an aqueous solution containing 15 grams of pigskin gelatin, having its iso-electric point at a pH of about 8.5, and 192 ml. of water at a temperature of 55 C. The oil was emulsified to a drop size of 2 to 5 microns. The emulsion was mixed with an aqueous solution containing grams of gum arabic and 81 ml. of water. The mixture was kept at a temperature above the gel point of the mixture. The mixture was diluted with 671 grams of water heated to a temperature of 55 C. Eleven (11) grams of a 5 weight percent aqueous solution of a copolymer of methylvinylether and maleic anhydride were then added to the waterdiluted mixture thereby forming a coacervatable mixture. The copolymer had a specific viscosity of 1.0 to 1.4. The specific viscosity was determined on a solution of 1 gm. of the copolymer in 100 ml. of methyl ethyl ketone at 25 C. The copolymer had a softening point temperature of 200 to 225 C. and a specific gravity of 1.37. The coacervatable mixture was at a pH of 9 and a temperature of about 55 C. An aqueous solution containing 14 weight percent of acetic acid was added, drop by drop, to the coacervatable mixture with continued agitation until the coacervatable mixture was at a pH of 4.6. A liquid capsular wall comprising gelatin, gum arabic, and a copolymer of methylvinylether and maleic anhydride in a dense state was deposited around clusters of the oil droplets by coacervate forces. The deposition of polymeric material occurred as a dense-liquid wall around individual clustered oil droplets to form encapsulated microcapsules. The wall material of the microcapsules contained gelatin as a dense liquid polymer complex with the copolymer of methylvinylether and maleic anhydride and the gum arabic. The microcapsules were now treated as solids dispersed in a residual aqueous medium.

The temperature of the aqueous dispersion of the microcapsules was then reduced to about 10 to 12 C. Ten (10) ml. of an aqueous solution containing 25 weight percent of glutaraldehyde was then added to the aqueous dispersion of microcapsules with continued agitation for several hours to thereby harden the microcapsules. The temperature of the aqueous dispersion of microcapsules was then permitted to rise to room temperature, about 22 C., over a period of 12 hours with continued agitation. The weight ratio of oil to gelatin of the microcapsules was on the order of 14:1 and the average diameter of the microcapsules was on the order of 8 to 12 microns. Aqueous solutions of the following were pre pared:

Solution 1.5 weight percent polyethyleneimine; filmforming polymeric material; marketed by the Dow Chemical Company, Midland, Mich., United States of America, under the trademark of Montrek 600E. The polyethyleneimine had a molecular weight of about 40,- 000 to 60,000, an assay of 33 weight percent minimum C H N, a density of 8.79 pounds per gallon at 25 C., a Brookfield Viscosity of 5000 at 25 C., a Brookfield Viscosity of 28 in a 5 weight percent aqueous solution, and a pH of 10 in a 5 weight percent aqueous solution.

Solution 2.2 weight percent dispersion of the microcapsules, containing a mark-forming material as an inner phase, prepared above.

Solution 3.--0.1 weight percent copolymer of methylvinylether and maleic anhydride; coacervate phase-inducing agent-pH of approximately 2; marketed by the GAP Corporation, New York, N.Y., United States of America, under the trademark of Gantrez AN139. The copolymer had a specific viscosity of 1.0 to 1.4. The specific viscosity was determined on a solution of 1 gm. of the copolymer in 100 m1. of methyl ethyl ketone at 25 C. The copolymer had a softening point temperature of 200 to 225 C. and a specific gravity of 1.37.

Solution 4.2 weight percent acetic acid.

A fabric ribbon woven from cotton was immersed for about 5 seconds in each of the above solutions in the order in which the solutions are numbered. The woven, fabric ribbon was then dried in air at a temperature of about F. The woven, fabric printing ribbon was tested for mark-forming performance by placing the woven, fabric printing ribbon in a typewriter along with a sensitized sheet of paper containing a coating of attapulgite clay. The woven, fabric printing ribbon was struck by the type of the typewriter and excellent marks were made on the sheet of paper indicating that the microcapsules were successfully bonded to the woven fabric ribbon.

The bonding of the microcapsules to the woven fabric ribbon was tested by immersing a portion of the woven fabric ribbon in water in the cup of an Osterizer mixer. The Osterizer mixer was run at low speed for about 30 seconds. The washed fabric printing ribbon was dried and then placed in a typewriter along with a sensitized sheet of paper in the manner dscribed above. The washed, fabric printing ribbon was struck by the type of the typewriter and excellent marks were made on the sheet of paper indicating that washing did not remove a significant amount of the microcapsules bonded to the woven fabric ribbon.

A woven fabric ribbon of cotton was immersed in Solution 1 which contained the film-forming polymeric material and in Solution 2 which contained the microcapsules and then was dried. A woven fabric ribbon of cotton was also immersed only in Solution 2 which contained only the microcapsules and then was dried. When tested for mark-forming performance in the manner described above, the woven fabric ribbons produced very poor marks on the sheet of paper. This indicates that there was very little bonding of the microcapsules to the woven fabric ribbons and that the novel bonding system of the present invention is necessary to produce the novel woven, fabric printing ribbons of the present invention.

Example II Microcapsules were bonded to woven fabric ribbons of nylon and silk in the same manner as described in Example I. The nylon fabric printing ribbon and the silk fabric printing ribbon were tested for mark-forming performance in the same manner as in Example I. Both woven, fabric printing ribbons produced excellent marks on their respective sheets of paper indicating that the microcapsules were successfully bonded to both the nylon and silk fabric printing ribbons. The print quality of the marks was comparable to that obtained with the cotton fabric printing ribbon in Example I.

What is claimed is:

1. A process for producing a woven, fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to its surface which comprises applying a polymeric material of one electric charge to the surface of a woven fabric ribbon; then applying microcapsules, containing a mark-forming material as an inner phase, to the surface of the woven fabric ribbon; and then substantially simultaneously with the application of the microcapsules, forming a coacervate of film-forming polymeric material at the surface of the woven fabric ribbon by applying a solution of an oppositely charged polymeric material to the surface of the woven fabric, the coacervate enveloping the microcapsules and wetting individual fibers at the surface of the woven fabric ribbon to thereby bond the microcapsules to individual fibers at the surface of the woven fabric ribbon; and thereafter drying the woven fabric ribbon to produce a woven, fabric printing ribbon having microcapsules bonded to its surface by means of a solidified coacervate polymeric material.

2. A process for producing a woven, fabric printing ribbon, comprised of individual fibers, having a multiplicity of rupturable microcapsules bonded to its surface which comprises applying microcapsules, containing a mark-forming material as an inner phase, to the surface of a woven fabric ribbon having a film-forming polymeric material of one electric charge present thereon; and then applying a coacervate phase-inducing agent of a solution of an oppositely charged polymeric material to the fabric ribbon to form a coacervate of film-forming polymeric material at the surface of the woven fabric ribbon, the coacervate enveloping the microcapsules and wetting individual fibers at the surface of the woven fabric ribbon to thereby bond the microcapsules to individual fibers at the surface of the woven fabric ribbon; and thereafter drying the woven fabric ribbon to produce a woven, fabric printing ribbon having microcapsules bonded to its surface by means of a solidified coacervate polymeric material.

3. The process of claim 2 wherein the coacervate of the film-forming polymeric material is a complex of a cationic polymeric material and an anionic polymeric material.

4. The process of claim 3 wherein the cationic polymeric material is polyethyleneimine and the anionic polymeric material is a copolymer of methylvinylether and maleic anhydride.

5. The process of claim 2 wherein the mark-forming material is an ink.

References Cited UNITED STATES PATENTS 3,418,250 12/1968 Vassiliades 1l736.2 3,509,173 4/1970 Lin 11736.2 3,533,958 10/1970 Yurkowitz 1l736.2

MURRAY KATZ, Primary Examiner US. Cl. X.R. l1736.2, 76 T 

